Infrared (IR) emission technique is an efficient technique for debugging very large scale integration (VLSI) integrated circuit (IC) devices, wherein IR emissions from an IC device during operation indicate drainage currents within the device. In this manner, IR emissions may be used to detect points with unexpected current consumption, and in particular points with unexpectedly high current consumption, thereby enabling localisation of a problematic design within the IC device. Estimation of a drainage current value is critical for distinguishing between a normal functional device and a problematic one; the current value being proportional to the ‘brightness’ (i.e. the amount of IR radiation emitted and other spectral characteristics) of the respective IR ‘hotspot’. For example, during normal operation an IC component may be biased to consume a constant level of current, such as may occur within a current mirror, voltage divider, etc. Additionally and/or alternatively, a leakage related emission may occur during normal operation, for example from ‘turned off’ transistor components. As such, it is important to be able to differentiate between such currents occurring during normal operation and drainage currents occurring from faulty behaviour.
However, the brightness of IR hotspots has not scaled proportionally with the scaling of modern IC devices. As such, although IR emission technique is still an effective technique for identifying high current flow within modern IC devices, the calibration of test equipment to determine current values based on the brightness of IR hotspots is becoming increasingly more difficult with the lower current values of modern IC devices. For example, typical leakage currents may be in the order of nA to several μA, depending on the bias conditions and expected behaviour. Identifying points with unexpected/irregular current consumption is particularly problematic when there are numerous IR emission hotspots located close to one another, since it is almost impossible to make an accurate current summation for each of the individual drainage sources therefor.